Which 'Mad Men' sex scene did January Jones disagree with?

January Jones is so loyal to "Mad Men" creator Matthew Weiner, she's only questioned his authority once.

Jones, who plays Don Draper's polarizing ex-wife Betty, said she sparred with Weiner when he wrote in a boozy hookup for her prim character, who circa the second season, was still married to the show's womaning ad man (Jon Hamm).

"Betty, at the end of season two, goes to a bar and winds up sleeping with a random guy. I didn't disagree with it; I just wanted to understand the motivation," Jones revealed in The Hollywood Reporter's Emmys roundtable discussion alongside Claire Danes, Emmy Rossum and other TV drama actresses.

"Is it revenge? And he explained to me that I needed to stop thinking. Betty is a sexual person -- she gets drunk and she gets laid. That's it. When it was explained that way, I was like, 'OK.' That's one of the beautiful things about 'Mad Men'; we're not given any time to think."

Jones, 34, also discussed a surprising twist in the AMC series' new season: her transition to Fat Betty, and the prosthetic padding required to achieve the illusion of the housewife's weight gain.

"I loved it. I didn't want to try to hide it, I thought it would become comical and weird," said Jones, who was pregnant with her son, Xander, at the time of filming. "And I also didn't want to have the character become pregnant because it just wouldn't make sense. It was definitely difficult, but I love what he did with the character's story."

But when she watched the episode, Jones confessed, she "paused it and went screaming into the other room. I got used to it."